Head-mounted display systems mount to the head of a user and allow the user to view the display or an image thereof. Generally, the display functions as a conveniently located interface with a computer, which may be included in the head-mounted display system. For example, a head-mounted display system may provide an aircraft pilot with maps and other information related to the real scene viewed by the pilot. Some head-mounted display systems allow the user to view a display image at the same time as viewing a real scene. See-through head-mounted display systems overlay a display image on a real scene viewed by the user. Recent advances in micro-optics manufacturing have resulted in the development of see-through head-mounted display systems targeted for the consumer market, where the display system may provide functionality similar to that of a smartphone. For example, U.S. Patent Application Publication No. US 2013/0021658 discusses a see-through head-mounted display system. Conventional head-mounted display systems are controlled by the user through a touch and/or voice control interface.